/* 引入网络字体（Poppins） */
@import url("http://fonts.googleapis.com/css?family=Poppins:200,300,400,500,600,700,800,900&display=swap");

*{
    box-sizing: border-box;
    font-family: "Microsoft YaHei UI", serif;
}
header{
    /* 固定定位 */
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    /* 弹性布局 */
    display: flex;
    /* 将元素靠边对齐 */
    justify-content: space-between;
    align-items: center;
    padding: 40px 100px;
    z-index: 1;
    /* 动画过渡 */
    transition: 0.6s;
}
header .logo{
    font-size: 32px;
    color: #fff;
    font-weight: 700;
    text-decoration: none;
    /* 转大写 */
    text-transform: uppercase;
    /* 字间距 */
    letter-spacing: 2px;
    transition: 0.6s;
}
header ul{
    display: flex;
    justify-content: center;
    align-items: center;
}
header ul li{
    list-style: none;
}
header ul li a{
    margin: 0 15px;
    text-decoration: none;
    color: #000;
    font-weight: 500;
    letter-spacing: 2px;
    transition: 0.6s;
}
.banner1{
    display: flex;
    position: relative;
    width: 100%;
    height: 80vh;
    background-color: #f5f5f5;
}
.banner2{
    position: relative;
    width: 100%;
    height:80vh;
    background-color: #f5f5f5;
}
.banner3{
    display: flex;
    position: relative;
    width: 100%;
    height: 200vh;
    background-color: #f5f5f5;
}
/* 鼠标滚动后，改变导航栏样式 */
header.sticky{
    padding: 6px 100px;
    background-color: #fff;
}
header.sticky .logo,
header.sticky ul li a{
    color: #000;
}

